Hydrocarbon elastomers

Hydrocarbon resins are used extensively as modifiers in adhesives, sealants, printing inks, paints and varnishes, plastics, road marking, flooring, and oil field appHcations. In most cases, they ate compounded with elastomers, plastics, waxes, or oils. Selection of a resin for a particular appHcation is dependent on composition, molecular weight, color, and oxidative and thermal stabiHty, as weU as cost. A listing of all hydrocarbon resin suppHers and the types of resins that they produce is impractical. A representative listing of commercially available hydrocarbon resins and their suppHers is included in Table 6. 

Cyclic Hydrocarbons. The cyclic hydrocarbon intermediates are derived principally from petroleum and natural gas, though small amounts are derived from coal. Most cycHc intermediates are used in the manufacture of more advanced synthetic organic chemicals and finished products such as dyes, medicinal chemicals, elastomers, pesticides, and plastics and resins. Table 6 details the production and sales of cycHc intermediates in 1991. Benzene (qv) is the largest volume aromatic compound used in the chemical industry. It is extracted from catalytic reformates in refineries, and is produced by the dealkylation of toluene (qv) (see also BTX Processing). 

Elastomers. Elastomers are polymers or copolymers of hydrocarbons (see Elastomers, synthetic Rubber, natural). Natural mbber is essentially polyisoprene, whereas the most common synthetic mbber is a styrene—butadiene copolymer. Moreover, nearly all synthetic mbber is reinforced with carbon black, itself produced by partial oxidation of heavy hydrocarbons. Table 10 gives U.S. elastomer production for 1991. The two most important elastomers, styrene—butadiene mbber (qv) and polybutadiene mbber, are used primarily in automobile tires. 

Rubbers. Plasticizers have been used in mbber processing and formulations for many years (8), although phthaHc and adipic esters have found Htde use since cheaper alternatives, eg, heavy petroleum oils, coal tars, and other predominandy hydrocarbon products, are available for many types of mbber. Esters, eg, DOA, DOP, and DOS, can be used with latex mbber to produce large reductions in T. It has been noted (9) that the more polar elastomers such as nitrile mbber and chloroprene are insufficiendy compatible with hydrocarbons and requite a more specialized type of plasticizer, eg, a phthalate or adipate ester. Approximately 50% of nitrile mbber used in Western Europe is plasticized at 10—15 phr (a total of 5000—6000 t/yr), and 25% of chloroprene at ca 10 phr (ca 2000 t/yr) is plasticized. Usage in other elastomers is very low although may increase due to toxicological concerns over polynuclear aromatic compounds (9). 

Antioxidants resistant to extraction by lubricants and gasoline are preferred for the stabili2ation of elastomers used in automotive appfications such as gaskets and tubing. Aromatic amine antioxidants, such as A/-phenyl-Ar-(p-toluenesulfonyl)-A-phenylenediamine [100-93-6] (37), with low solubifity in hydrocarbons, are extracted slowly from elastomers and are used for these appfications. 

Materials of Construction. GeneraHy, carbon steel is satisfactory as a material of construction when handling propylene, chlorine, HCl, and chlorinated hydrocarbons at low temperatures (below 100°C) in the absence of water. Nickel-based aHoys are chiefly used in the reaction area where resistance to chlorine and HCl at elevated temperatures is required (39). Elastomer-lined equipment, usuaHy PTFE or Kynar, is typicaHy used when water and HCl or chlorine are present together, such as adsorption of HCl in water, since corrosion of most metals is excessive. Stainless steels are to be avoided in locations exposed to inorganic chlorides, as stainless steels can be subject to chloride stress-corrosion cracking. Contact with aluminum should be avoided under aH circumstances because of potential undesirable reactivity problems. 

Because of the unusual reactivity of the DCPD molecule, there are a number of wide and varying end use areas. The primary uses in the U.S. are DCPD-based unsaturated polyester resins (36%) hydrocarbon type resins, based on DCPD alone or with other reactive olefins (39%) EPDM elastomers via a third monomer ethylidenenorhornene or DCPD (16%) and miscellaneous uses (9%), including polychlorinated pesticides, polyhalogenated flame retardants, and polydicyclopentadiene for reaction injection mol ding (39). 

The process yields a random, completely soluble polymer that shows no evidence of crystallinity of the polyethylene type down to —60°C. The polymer backbone is fully saturated, making it highly resistant to ozone attack even in the absence of antiozonant additives. The fluid resistance and low temperature properties of ethylene—acryUc elastomers are largely a function of the methyl acrylate to ethylene ratio. At higher methyl acrylate levels, the increased polarity augments resistance to hydrocarbon oils. However, the decreased chain mobiUty associated with this change results in less fiexibihty at low temperatures. 

Chemical Resistance. Fluorocarbon elastomer compounds show excellent resistance to automotive fuels and oils, hydrocarbon solvents, aircraft fuels and oils, hydrauHc fluids, and certain chlorinated solvents, and may be used without reservation. 

Compounding. Owing to the number of ingredients required in a conventional mbber recipe, fluorocarbon elastomer compounding seems simple compared to typical hydrocarbon elastomer recipes. However, the apparent simplicity of such formulations makes a selection of appropriate... 

Two elastomers have been commercialized with unique property profiles. One has fluoroalkoxy substituents that provide resistance to many fluids, especially to hydrocarbons. This material also has a broad use temperature range and useful dynamic properties. Aryloxy substituents provide flame retardant materials without halogens. 

FZ elastomers have excellent resistance to hydrocarbons and inorganic acids as expected for a fluoriaated elastomer. They are strongly affected by polar solvents, but are more resistant to amines than most other fluoriaated elastomers as showa ia Table 2. 

All these elastomers, especially poly(ethylene- (9-butylene) and poly(ethylene- (9-propylene), are nonpolar. The corresponding block copolymers can thus be compounded with hydrocarbon-based extending oils, but do not have much oil resistance. Conversely, block copolymers with polar polyester or polyether elastomer segments have Htde affinity for such hydrocarbon oils and so have better oil resistance. 

Oil resistance demands polar (non-hydrocarbon) polymers, particularly in the hard phase. If the soft phase is non-polar but the haid phase polar, then swelling but not dissolution will occur (rather akin to that occurring with vulcanised natural rubber or SBR). If, however, the hard phase is not resistant to a particular solvent or oil, then the useful physical properties of a thermoplastic elastomer will be lost. As with all plastics and rubbers, the chemical resistant will depend on the chemical groups present, as discussed in Section 5.4. 

Thermoplastic block copolymers were used for pressure-sensitive and hot-melt rubber adhesives as from the middle sixties. These adhesives found application in packaging, disposable diapers, labels and tapes, among other industrial markets. The formulation of these adhesives generally includes an elastomer (generally containing styrene endblocks and either isoprene, butadiene or ethylene-butylene midblocks) and a tackifier (mainly a rosin derivative or hydrocarbon resin). 

Rosin esters show low cloud points and would have wide compatibility with most elastomers. Aliphatic hydrocarbon resins, however, will only be compatible with aliphatic elastomers (e.g. natural rubber). 

The chemical nature of the tackifier also affects the compatibility of resin-elastomer blends. For polychloroprene (a polar elastomer) higher tack is obtained with a polar resin (PF blend in Fig. 27) than with a non-polar resin (PA blend in Fig. 27). Further, the adhesion of resin-elastomer blends also decreases by increasing the aromatic content of the resin [29]. Fig. 28 shows a decrease in T-peel strength of styrene-butadiene rubber/polychloroprene-hydrocarbon resin blends by increasing the MMAP cloud point. Because the higher the MMAP... 

The plastics industry was launched nearly 150 years ago with the production of certain derivatives of cellulose. However, its real emergence as a growth industry of immense proportions and importance has occurred since World War II with the sustained strong growth of thermoplastics and specialty elastomers. The importance of the polymers industry in modern society is underscored by the myriad of uses already developed for these materials, with more being developed almost daily. Although there are a multitude of polymers that are derived from hydrocarbons, we will only briefly discuss the more common thermoplastics that are made from relatively simple monomers from petroleum. 

Ceramic materials have found acceptance as cyclone liners for the apex orifice as well as other areas which exhibit severe abrasion. These include areas such as the lower cone liner and vortex finder. Nihard has also proven to be an acceptable wear material, especially for vortex finders and other areas which require strength as well as abrasion resistance. Other elastomer materials such as neoprene and nitrite are also utilized when hydrocarbons are present or when the temperature exceeds 60 °C. Urethane has found acceptance, especially in areas where the solids are relatively fine,... 

Ruorocarbon elastomers are convemently divided mto three groups (1) the most widely used group of copolymers of VDF and one or two perfluoroolefins, (2) a less widely used group based on TFE and simple hydrocarbon olefins, and (3) a much smaller group compnsmg copolymers of TFE and jierfluoroolefms [/, 7, 30]... 

Both the dipolymers and terpolymers have excellent resistance to hydrocarbons found m petroleum-based fuels and lubricants The 69 5% F terpolymer resists swellmg m blended fuels that contain metlianol and can be used in contact with certain phosphate ester-based hydraulic fluids Terpolymers are preferred for contact with aromatic solvents, although either type performs well in higher alcohols VDF-based elastomers dissolve m polar aprotic solvents such as ketones, esters, amides, and certam ethers These elastomers are therefore not suitable for contact with fluids that contain substantial amounts of these solvents because of excessive swell and consequent loss of mechanical properties... 

The elastomer of the stator can be damaged by high temperatures and some hydrocarbons. 

Polyisoprene is a synthetic polymer (elastomer) that can he vulcanized hy the addition of sulfur. cis-Polyisoprene has properties similar to that of natural ruhher. It is characterized hy high tensile strength and insensitivity to temperature changes, hut it has low abrasion resistance. It is attacked hy oxygen and hydrocarbons. 

---